Robust data storage systems typically utilize multiple computing devices and different types of storage devices (e.g., hard disk drives, optical disk drives, solid state drives, or tape drives) to hold large amounts of data while also enabling high availability and resilience to hardware or other failures. Generally speaking, individual storage systems can be classified according to their latency and/or throughput. For example, a high speed storage system may use very fast hard disk drives, solid state drives, and caches to maximize throughput and minimize latency. However, employing fast storage devices can be prohibitively expensive for storing large amounts of data. A low speed storage system employs cheaper media types (e.g., slower hard disk drives, hard disk drives that conserve energy by powering down, tape drives, optical drives, etc.) to reduce costs, but they provide lower throughput and higher latency.
These low speed storage systems can also employ deduplication technology to increase the amount of data they can store in the same amount of storage space. Deduplication is a technique similar to compression for reducing or eliminating duplicate copies of data. As an example, when two files or objects share some common data, deduplication may store the common data only once. In some implementations, repeating clusters of data may be replaced with a small reference to the location where the repeated data is stored. This compression technique can be used to improve storage utilization and reduce network bandwidth usage.
Tape drives are another storage-efficient technology for low speed storage systems. An enterprise tape library apparatus is a data storage device that provides sequential storage of objects comprising items of data on different magnetic tapes. When a request for one of the objects is received, the corresponding magnetic tape is identified, loaded on one of the tape drives, and physically wound to read the object in the enterprise tape library apparatus. A tape drive provides sequential access storage, unlike hard disk drives or solid state drives that are designed to provide random access storage. A disk drive can move to any position on the disk in a few milliseconds, but a tape drive must physically wind tape between reels to read any one particular piece of data or write to a specific place. As a result, tape drives have very slow average seek times to data and are typically configured to write data sequentially.